Safety systems such as a PCS (Pre-Crash Safety System) have been developed for avoidance, or for reducing damage caused by a collision. With such a safety system, a warning is outputted when a preceding vehicle approaches the host vehicle. However if the timing of the warning is too early, then there is a risk that the outputting of the warning may interfere with operations performed by the driver of the host vehicle for avoiding the object, and may cause a feeling of unease to the driver.
With the patent of PTL 1, a history is accumulated of the timings at which avoidance operations were performed by the driver at occasions when prescribed distances were reached between the host vehicle and preceding vehicles. A warning is given to the driver based on comparing an actual operation performed by the driver with the accumulated history of timings of avoidance operations. It is intended in that way to prevent interference between the timing of outputting a warning and the timing of an operation performed by the driver for avoiding an object.